It depends on several things. For example the users on linux and windows are different (probably), you need to use the user/password of the target system.
The user you entered has really no right to write into that directory. Probably you can check the log file of the sshd (which one have you installed?)
Do not use \ on linux, if you want to enter windows-like path, use double backslashes: c:\\something\\dir\\Desktop. Also use ' to avoid mishandling of your path:
scp filename.txt 'barathan.rajalingam@host:c:\\users\\barathan.rajalingam\\Desktop'
You can also configure passwordless login, just google "passwordless ssh login windows" and follow the steps.